MASSMUTUAL FUNDS

MassMutual U.S. Government Money Market Fund

Supplement dated September 23, 2025 to the

Prospectus dated February 1, 2025, as Revised on February 5, 2025, and the

Summary Prospectus dated February 1, 2025

This supplement provides new and additional information beyond that contained in the Prospectus and Summary Prospectus, and any previous supplements. It should be retained and read in conjunction with the Prospectus and Summary Prospectus, and any previous supplements.

Effective September 5, 2025 (the “Termination Date”), the MassMutual U.S. Government Money Market Fund (the “Fund”) was dissolved pursuant to a Plan of Liquidation and Termination, approved by the Board of Trustees of the MassMutual Premier Funds. Shareholders of Class R5 shares of the Fund received proceeds in proportion to the number of Class R5 shares held by each of them on the Termination Date.

PLEASE RETAIN THIS SUPPLEMENT FOR FUTURE REFERENCE

PREMPRO-25-16

USGOVMM-25-04